According to two separate people with direct knowledge of the transaction, Viddy’s Series B* was raised at a valuation of approximately $300 million. [See update below.] This is heady territory, even in the wake of Instagram’s recent stratospheric acquisition.

The company’s $1.5 million seed round closed around April 2011 and, according to my sources, was priced at $16 million. That’s a 20-times multiple in just twelve months for a company that has not monetized to any significant degree.

Viddy has displayed some impressive growth without question. It recorded more than 5.5 million downloads in an 11 day period ending last week, bringing its total to more than 10 million. Also, the iPhone only service has yet to expand to the Android platform or add tablet specific optimization, although both things are said to be on its roadmap for the coming year.

With no sign of its growth slowing, maybe we’ll look back at this transaction as a steal. This would be likely, of course, should Google or Twitter look to acquire the growing video service.

Update: Shortly after publishing this post, PandoDaily learned from sources close to the transaction that the actual valuation was approximately $370 million, outpacing even our most aggressive estimates.

*An early version of this post incorrectly labeled the round as a Series A, rather than a Series B financing.